I have the same issue. With the newest firmware I am unable to calibrate the frame imu. The gimbal works fine if I disconnect the frame imu, but I would love to be able to use both sensors.
If they do not have address jumper, you can not use them as frame IMU (unless one of them is already at factory set as frame IMU). Did the IMUs come with the 32 bit board? You should get IMUs that are meant for 32 bit board.
I ordered another 32bit controller. It came with the original 32bit imu. Removed the address jumper. Works fine. I noticed that the earlier modules are built better. Better fiberglass boards and better soldering. One difference is the mini usb connector.